Single-instruction multiple-data (SIMD) processors are characterized by having an array of processors that perform the same operation simultaneously on every element of a data array. Vector processing, an application of SIMD processors, uses vector instructions, which specify the operation to be performed and specify the list of operands, i.e., the data vector, on which it will operate.
The use of processor arrays and vector processing can result in extensive parallelism, resulting in high execution speeds. Yet, despite impressive execution speeds, getting data in and out of the processor can be a problem. Execution speeds are less useful if input/output speeds cannot keep up.
In many applications, such as video processing, real-time processing speed is desirable. Yet, a stumbling block to real-time processing is the large amount of data that must be processed to generate the pixels, lines, and frames of a video picture.
A need exists for an easily manufactured SIMD processor that maximizes data input rates without increasing manufacturing costs. Although the need for such processors is not limited to television, digital television processing involves processing tasks, such as scan rate conversion, for which a processor with a fast throughput is desirable.
With regard to scan rate conversion, television relies on the concept that a picture can be broken down into a mosaic suitable for transmitting and then reassembled to produce a television picture. This process is accomplished with linear scanning. The television picture is scanned in a sequential series of horizontal lines, at both the transmitting and receiving end of the television system.
Various geopolitical regions have different scanning standards. The United States uses the National Television Systems Committee (NTSC) standard. Each picture, i.e., frame, has 525 lines. These lines are interlaced to make two fields having 262.5 lines each, and each field is scanned at a rate of 60 fields per second. Some countries use a Phase Alternate Line (PAL) system, which has similar characteristics. Other countries use a Sequential Color and Memory (SECAM) system, in which 625 lines make up a frame. The lines are interlaced to make two fields having 312.5 lines each, and each field is scanned at a rate of 50 fields per second.
If a scan rate is too slow, the viewer will notice a large area flicker. The 60 Hz and 50 Hz standard scan rates are intended to exceed a rate at which flicker is annoyingly noticeable, but not place expensive technological demands on the receiving system. Nevertheless, faster scan rates are desirable for improved viewing.
In addition to scan rates, another factor in picture quality is the number of lines per frame, i.e., vertical resolution. If there are too few lines, the distinction between each line is perceptible. Like scan rate standards, the selection of a standard number of lines per field is intended to surpass the viewer's annoyance level without unduly burdensome technological costs. Yet, like faster scan rates, higher line per field ratios are desirable for improved viewing.
Recent developments in television systems include digital processing within the receiver to convert scan characteristics, such as scan rates and lines per field. Yet, existing digital receivers process data serially, and because of processing throughput limitations of serial systems, the pixel resolution is limited. A need exists for a television receiving system that receives an incoming signal with one set of scan characteristics and generates a picture with different scan characteristics. The processing throughput should not unduly constrain the level of pixel resolution.